Decontamination and recovery of a nuclear facility to allow continued operation

A power supply failure caused a loss of power to key ventilation systems in an operating nuclear facility. The in-cell depression was lost, which led to an egress of activity through prepared areas and into the normal operating areas. After an initial programme of radiological monitoring to quantify and categorise the activity in the operating areas, a plan was developed for the decontamination and remediation of the plant. The scope of the recovery plan was substantial and featured several key stages. The contamination was almost entirely ¹³⁷Cs, reflecting the α:β/γ ratio for the facility. In addition to the physical remediation work, several administrative controls were introduced such as new local rules, safety signage to indicate abnormal radiological conditions in certain areas and training of the decontamination teams. All areas of plant, which were contaminated, were returned to normal access arrangements and the plant was successfully returned to full operational capability, <12 months from the date of the event. (authors)